1. Field of the Invention
The present invention relates to a solid-state image sensing apparatus in which a plurality of unit pixels are arranged, and a signal from each unit pixel can be arbitrarily selected and read out by address control.
2. Description of the Related Art
In an amplified solid-state image sensing device (also called APS; active pixel sensor/gain cell), which is a kind of X-Y addressing-type solid-state image sensing device, pixels are composed using active devices having a MOS structure, etc. (MOS transistors) in order to have an amplification function in pixels themselves. Specifically, signal electric charge stored in a photodiode, which is a photoelectric transfer device, is amplified by the active device, and is read out as image information.
In an X-Y addressing-type solid-state image sensing device, for example, a large number of pixel transistors are arranged in a two-dimensional matrix to constitute a pixel area. Storage of signal electric charge corresponding to incident light is started for each line (row) or for each pixel. The signal of electric current or voltage based on the stored signal electric charge is read out in sequence from each pixel by addressing (for example, refer to Japanese Unexamined Patent Application Publication Nos. 11-239299, 2001-069408, 2001-298748 and 2003-031785). For example, in a VGA format of 300 thousand pixels, 30 pieces of images are output per one second, which appears smooth animation to human eyes at an output rate of 12 MHz.
Meanwhile, in recent years, it is expected that images are output at 30 pieces/second using, for example, an image sensing device having ultra-many pixels. In specific examples, images are output at 30 pieces/second from a solid-state image sensing apparatus having 3 million pixels or 30 million pixels. Also, when high time resolution is required, such as in the case of a car collision experiment or monitoring an impact moment of a ball hit by a baseball batter, it is necessary to output 100 to 10 thousand pieces of images per one second.
Here, as a method of satisfying the above-described requirements at a low data rate, a method of increasing output terminals, providing hundreds of output terminals, and outputting signals in parallel is considered.
However, in that case, the number of output terminals becomes large, and thus various problems arise. For example, the area of the solid-state image sensing apparatus becomes large (increases cost), the ICs in the next stage becomes large by the increase of input terminals, the implementation becomes difficult, miniaturization of the camera becomes difficult, the synchronization of so many output terminals is difficult, and the outputting at a high clock rate is difficult due to the difficulty of synchronization.
As a method of improving these problems, an increase in read-out speed is considered. In this case, for example, in order to output images at 30 pieces/second from a solid-state image sensing apparatus having 3 million pixels or 30 million pixels, the operation becomes 120 MHz or 1.2 GHz, individually. Also, when a high time resolution is required, for example, in the case of outputting 1,000 to 10,000 pieces of images, increasing the read-out speed is effective.
However, if the read-out speed is simply increased, problems, such as an increase in power consumption, noises, unnecessary radiation, might occur.